[IMP] shop: added openchatter on product shop

- product.template now inherits from mail.thread
- added opencahtter on product.template form view
- added discussion thread + attachments in product website view
- added file_type field on ir_attachment, that replaces the javascript thing
from mail.js
- added a controller to comment a product.template
[IMP] website_sale: website chatter: some styling on the attachments
[MERGE] [IMP] shop: added openchatter on product shop

- product.template now inherits from mail.thread
- added opencahtter on product.template form view
- added discussion thread + attachments in product website view
- added file_type field on ir_attachment, that replaces the javascript thing
from mail.js
- added a controller to comment a product.template
- added a css file for the openchatter embedded in the product website view
[IMP] website_sale: product website chatter: added a title-link for the comment section
[FIX] portal_gamification: fixed references to group_portal in gamification.
Indeed gamification is a new module that landed in trunk recently. It makes some
references to the portal group. However this group has been moved into the
base module in this website feature branch. The references have therefore
been updated.
[FIX] website_sale: product template
- fixed link to comments
- fixed Comments title + comment form not visible if no previous discussion on the prodcut